Research On Long Stroke Fast Tool Servo System Based On Aerostatic Guideway

In recent years,optical freeform surfaces have been widely used in many fields.However,they have complex non-rotational symmetrical structures and are difficult to process.With the development of ultra-precision machining technology,diamond turning technology has become an effective method for processing optical freeform surfaces.However,the slow tool servo system has the problem of low processing efficiency,and the fast tool servo device based on flexible hinges cannot process optical freeform surfaces with a height difference of millimeters.Therefore,it is necessary to develop a fast tool servo system with long stroke and high frequency response.The main contents of this thesis are as follows:(1)Design and optimize the long stroke fast tool servo device.First,the design of the long stroke fast tool servo device is carried out,and the structure of the porous aerostatic guideway driven by the voice coil motor is researched and adopted.Then the statics and dynamics modules in ANSYS were used to simulate and compare the commonly used T-shaped guideway and square guideway respectively,and the scheme of using square guideway was determined,and the square guideway structure was further optimized.Then the performance simulation of the fixed guideway is carried out to verify the feasibility of the scheme.Finally,the overall design of the long stroke fast tool servo device is completed.(2)The drive system of the long stroke fast tool servo device is designed.First,the calculation and analysis are carried out according to the performance requirements of the long stroke fast tool servo system,and the voice coil motor that meets the requirements is determined.Then according to the calculation and analysis of the motor parameters,select the driver and power supply that meet the requirements,and then select the grating scale as the position detection element of the system through comparison and analysis.Finally,determine the controller used in this system.(3)Simulation analysis and testing of the developed long stroke fast tool servo device.First,the static model of the aerostatic guideway was established,and then the static stiffness of the porous aerostatic bearings were tested.The test results showed that when the gas film thickness is 10μm,the static stiffness of the aerostatic bearing is about 27N/μm.According to the statics model,the stiffness of the aerostatic guideway was simulated and analyzed,and then the static stiffness of the fast tool servo device was tested.The results showed that the vertical and horizontal static stiffness of the fast tool servo device were 26.6N/μm and 25.6N/μm respectively.The experimental results verify the correctness of the simulation analysis.(4)Carried out the research on the performance test of the long stroke fast tool servo system.The Simulink module is used to compare and study the control algorithm of the long stroke fast tool servo system,and test the control accuracy of the fast tool servo system.The research results show that the rise time of the step response of the system is 3.9ms,and the overshoot is 5.2% of the stroke.The position keeping test result shows that the steady-state error PV of the system is 14 nm.In the sine trajectory tracking test with a movement stroke of 5mm and a movement frequency of 40 Hz,the tracking error of the system is about 13μm.The motion resolution test shows that the motion resolution of the system is better than10 nm.Using a spectral confocal sensor to test,the test results manifest that the positioning accuracy of the fast tool servo system is about 0.357μm,and the repeat positioning accuracy is about 0.089μm.